Chemistry is a branch of science that has been around for a long
time. In fact, chemistry is known to date back to as far as the
prehistoric times. Due to the amount of time chemistry takes up on
the timeline, the science is split into four general chronological
categories. The four categories are: prehistoric times - beginning of
the Christian era (black magic), beginning of the Christian era - end
of 17th century (alchemy), end of 17th century - mid 19th century
(traditional chemistry) and mid 19th century - present (modern
chemistry).

Alchemists not only wanted to convert metals to gold, but
they also wanted to find a chemical concoction that would
enable people to live longer and cure all ailments. This
elixir of life never happened either.

End of 17th Century

Death of Alchemy

The disproving of Aristotle's four-elements theory and
the publishing of the book, The Skeptical Chemist (by
Robert
Boyle), combined to destroy this early form of
chemistry.

Johann J. Beecher believed in a substance called
phlogiston.
When a substance is burned, phlogiston was supposedly added
from the air to the flame of the burning object. In some
substances, a product is produced. For example, calx of
mercury plus phlogiston gives the product of mercury.

Charles
Coulomb discovered that given two particles separated by
a certain distance, the force of attraction or repulsion is
directly proportional to the product of the two charges and
is inversely proportional to the distance between the two
charges.

1774-1794

Disproving of the Phlogiston Theory

Joseph
Priestley heated calx of mercury, collected the
colorless gas and burned different substances in this
colorless gas. Priestley called the gas "dephlogisticated
air", but it was actually oxygen. It was Antoine
Lavoisier who disproved the Phlogiston Theory. He
renamed the "dephlogisticated air" oxygen when he realized
that the oxygen was the part of air that combines with
substances as they burn. Because of Lavoisier's work,
Lavoisier is now called the "Father of Modern
Chemistry".

1803

Dalton's Atomic Theory

John
Dalton publishes his Atomic Theory which states that all
matter is composed of atoms, which are small and
indivisible.

William
Crookes made headway in modern atomic theory when he
used the vacuum tube made by Heinrich Geissler to discover
cathode rays. Crookes created a glass vacuum tube which had
a zinc sulfide coating on the inside of one end, a metal
cathode imbedded in the other end and a metal anode in the
shape of a cross in the middle of the tube. When electricity
was run through the apparatus, an image of the cross
appeared and the zinc
sulfide glowed. Crookes hypothesized that there must
have been rays coming from the cathode which caused the zinc
sulfide to fluoresce and the cross to create a shadow and
these rays were called cathode rays.

Eugene Goldstein discovered positive particles by using a
tube filled with hydrogen gas (this tube was similar to
Thomson's tube...see 1897). The positive particle had a
charge equal and opposite to the electron. It also had a
mass of 1.66E-24 grams or one atomic mass unit. The positive
particle was named the proton.

1895

X-rays

Wilhelm
Roentgen accidentally discovered x-rays while
researching the glow produced by cathode rays. Roentgen
performed his research on cathode rays within a dark room
and during his research, he noticed that a bottle of barium
platinocyanide was glowing on a shelf. He discovered that
the rays that were causing the fluorescence could also pass
through glass, cardboard and walls. The rays were called
x-rays.

1896

Pitchblend

Henri
Becquerel was studying the fluorescence of pitchblend
when he discovered a property of the pitchblend compound.
Pitchblend
gave a fluorescent light with or without the aid of
sunlight.

J.J.
Thomson placed the Crookes' tube within a magnetic
field. He found that the cathode rays were negatively
charged and that each charge had a mass ratio of 1.759E8
coulombs per gram. He concluded that all atoms have this
negative charge (through more experiments) and he renamed
the cathode rays electrons. His model of the atom showed a
sphere of positively charged material with negative
electrons stuck in it. Thomson received the 1906 Nobel
Prize in physics.

Marie
Curie discovered uranium and thorium within pitchblend.
She then continued to discover two previously unknown
elements: radium and polonium. These two new elements were
also found in pitchblend. She received two nobel prizes for
her discovery; one was in chemistry while the other was in
physics.

1909

Mass of the Electron

Robert
Millikan discovered the mass of an electron by
introducing charged oil droplets into an electrically
charged field. The charge of the electron was found to be
1.602E-19 coulombs. Using Thomson's mass ration, Millikan
found the mass of one electron to be 9.11E-28 grams.
Millikan received the 1932 Nobel Prize in Physics for this
discovery.

1911

Three Types of Radioactivity

Ernest
Rutherford sent a radioactive source through a magnetic
field. Some of the radioactivity was deflected to the
positive plate; some of it was deflected to the negative
plate; and the rest went through the magnetic field without
deflection. Thus, there were three types of radioactivity:
alpha
particles (+), beta
particles (-) and gamma
rays (neutral). By performing other experiments and
using this information, Rutherford created an atomic model
different from Thomson's. Rutherford believed that the atom
was mostly empty space. It contains an extremely tiny, dense
positively charged nucleus (full of protons) and the nucleus
is surrounded by electrons traveling at extremely high
speeds. The Thomson model was thrown out after the
introduction of the Rutherford model.

1914

Protons within a Nucleus

Henry
Moseley attempts to use x-rays to determine the number
of protons in the nucleus of each atom. He was unsuccessful
because the neutron had not been discovered yet.

Enrico
Fermi bombards elements with neutrons and produces
elements of the next highest atomic number. Nuclear
fission occurred when Fermi bombarded uranium with
neutrons. He received the 1938 Nobel Prize in physics.

1934

Artificial Radioactive Elements

Irene
Curie and Frederic Joliot-Curie discovered that
radioactive elements could be created artificially in the
lab with the bombardment of alpha particles on certain
elements. They were given the 1935 Nobel Prize.

Albert
Einstein and Enrico Fermi both warned the United States
about Germany's extensive research on atomic fission
reaction. Below the football field at the University
of Chicago, the United States developed the very first
working nuclear fission reactor. The Manhattan Project was
in process.

Each link for each time interval contains some information about
that period. Unfortunately, the information is sparse and the
presentation of the info leaves much to be desired. However, more
information on chemical history can be found in the links listed
below. The list is collated in a chronological manner so like the
table above, alchemy and black magic should be on top while
traditional and modern chemistry should be closer to the end of the
list. Also, there are some other links besides the ones that are in
the time-interval section and these links should lead you to more
information about the underlined topics.

Additional History Links

1. Alchemy
- this link provides an insight into the science that was said to precede chemistry.
It gives a brief, colorful history of alchemy itself and a few stories about
the people who actually practiced the science.

2. More
Alchemy....a lot more - a whole website dedicated to the predecessor
of chemistry. This site contains unlimited information about alchemy. If you
have questions about alchemy, this is definitely the place to go!

3. THE
History of Chemistry - a great cache of chemical history is contained
at this Umea University Chemistry Department site. Biographies of famous scientists,
collection of science papers and etc. are found and well-catalogued in this
area.

4. The
Week in Chemical History - this site makes a connection between the
current week and an important episode in the past that had a great impact on
the world of chemistry

5. Chemistry
Papers - this site not only provides a great amount of papers on
certain chemistry theories, but it also contains many papers written on topics
in the other sciences. In fact, the papers are collected and collated by their
scientific topics (chemistry, physics, biology)

6. African
American Scientists - contains a list of African American scientists
who have made a difference in each of their respective sciences.